This invention relates to guns for perforating oil well casing, and more particularly, it relates to the barrel portion of a perforating gun and the manner in which the sections of the gun barrel are interconnected in an end-to-end arrangement.
In a perforating gun, explosive charges are employed in an elongated barrel, with the charges being directed radially outward therefrom. The elongated barrel is formed by a plurality of tubular sections that are interconnected in an end-to-end arrangement. One manner of interconnecting the tubular sections to form the gun barrel is that of using threaded connections to interconnect the ends of adjacent tubular sections. Another manner of coupling adjacent tubular sections together to form an elongated barrel involves the use of a coupling section between adjacent tubular sections. See, for example, U.S. Pat. No. 3,528,511 to Boop et al.
Coupling sections utilized to interconnect adjacent tubular sections in a perforating gun barrel, such as that shown in Boop, have been cylindrically shaped members having a midsection that is of an outside diameter equal to the outside diameter of the tubular gun barrel sections. On each side of the midsection portion, the member is cylindrically shaped with an outside diameter that is equal to the inside diameter of the tubular gun barrel sections, such that the coupling section ends are insertable into the open ends of adjacent barrel sections. A number of bolts, typically four, are used to secure the end of a tubular section to an end of the coupling section.
This conventional bolt-together manner of interconnecting tubular sections to form a perforating gun barrel presents a number of attendant undesirable features. For example, the use of a coupling section that spaces apart the ends of adjacent tubular sections produces a wider spacing of the explosive charges at the coupling section locations resulting in a nonuniformity of perforation of a casing. Accordingly, fewer charges per unit of length of the gun barrel can be accommodated and a larger and heavier perforating gun is thus required to produce a given extent of perforation. Another attendant disadvantage to the described manner of coupling gun barrel sections together is that the stress of an explosion is borne almost exclusively by the coupling section between the adjacent barrel sections. The absorption of a substantial amount of the explosion-induced stress is by the connecting bolts and midsection portion of the coupling section, which can be deformed as a result and make the disassembling of the gun barrel for reloading difficult and the useful life of the coupling section relatively short.
Accordingly, it would be desirable to provide a means of interconnecting tubular sections to form an elongated perforating gun barrel that would permit the explosive charges to be uniformly distributed along the entire length of the barrel without gaps and which would distribute the stress of an explosion to the tubular sections, therefore providing a more efficient and economical perforating gun.